Defence Against Disease

The innate immune system is the first line of defence against disease in animals.
It includes physical and chemical barriers such as the skin, mucous membranes and stomach acid.
The innate immune response is non-specific, meaning it works against a wide range of disease-causing agents (pathogens).
This system also includes phagocytic cells, such as macrophages and neutrophils, which engulf and destroy invading pathogens.
The inflammatory response, where blood vessels dilate and become more permeable to allow white blood cells to reach the site of infection, is also part of innate immunity.
The innate immune system acts quickly, often within minutes to hours of an infection beginning.

The adaptive immune system is more specific and slower than the innate immune system, involving components like T cells and B cells.
B cells produce antibodies, proteins that recognise and bind to specific antigens on the surface of pathogens.
Antibodies neautralise pathogens, marking them for destruction by other immune cells or preventing them from entering cells.
T cells help to regulate the immune response or kill infected cells directly. Helper T cells stimulate B cells to produce antibodies, while cytotoxic T cells destroy infected cells.
There is a memory attribute associated with the adaptive immune system. After initial exposure to an antigen, some B and T cells become memory cells and can initiate a faster and stronger immune response if the same antigen is encountered again.

Vaccination is a method used to stimulate the adaptive immune response and create an immunological memory without causing disease.
Vaccines provide a form of artificial immunity, tricking the body into thinking it has encountered a pathogen so it generates an immune response.
Often made from weakened or inactivated forms of pathogens, vaccines expose the immune system to antigens that belong to the pathogen, allowing the production of specific antibodies.
If the animal encounters the actual pathogen later, the immune system can respond quickly and effectively thanks to the memory cells produced following vaccination.

Antimicrobials are used to kill microorganisms or inhibit their growth.
Examples of antimicrobials include antibiotics (active against bacteria), antifungals (against fungi), and antivirals (against viruses).
Not all types of antimicrobials kill the pathogens; some simply inhibit their growth, allowing the immune system more time to destroy them.
Meanwhile, antiparasitics work against parasites, and are often specific for certain types of parasites.
It’s essential to use antimicrobials and antiparasitics responsibly as misuse can lead to the development of resistance in the pathogens.